ASCO: Early RT Hikes Risk for Breast Cancer

Action Points

This study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.

Girls treated with chest radiation for childhood cancers have an elevated risk of breast cancer later, even if the radiation dose was relatively small.

Point out that for women exposed to the high levels of mantle radiation formerly used to treat Hodgkin lymphoma (20 Gy or more), the cumulative incidence of breast cancer (31%) is similar to that seen in BRCA1/2 mutation carriers.

CHICAGO -- Girls treated with chest radiation for childhood cancer have an elevated risk of breast cancer later, even if the radiation dose was relatively small, a researcher said here.

With a median follow up of 26 years, 175 of the nearly 1,300 cancer survivors later developed breast cancer at a median age of 38 years. The time between the initial therapy and later breast cancer was a median of 23 years, the researchers found.

It has been known for some time that intensive radiation for Hodgkin's lymphoma in childhood increases the risk of breast cancer, according to Chaya Moskowitz, PhD, of Memorial Sloan-Kettering Cancer Center in New York City.

But how that risk factor compares to others risk factors, such as carrying certain mutations, has been unclear, Moskowitz told reporters at the annual meeting of the American Society of Clinical Oncology (ASCO).

It has also not been clear how lower doses of radiation used to treat other childhood cancers affect breast cancer risk, she said.

To find out, her group analyzed data from 1,268, 5-year cancer survivors in the Childhood Cancer Survivor Study, which allowed calculation of the cumulative incidence of breast cancer after radiation therapy.

As well, they studied 4,570 first-degree female relatives of participants in the Women's Environmental Cancer and Radiation Epidemiology study to estimate the incidence associated with carrying two mutations, BRCA1 and BRCA2, that increase the risk of breast cancer.

Overall, Moskowitz said the cumulative incidence of breast cancer at age 50 was 24%, compared with the 4% background rate among all women reported by the Surveillance and Epidemiology End Results (SEER) database.

For women exposed to the high levels of mantle radiation formerly used to treat Hodgkin lymphoma (20 Gy or more), the cumulative incidence at age 50 was higher at 31%, Moskowitz said.

That is similar to the 30% incidence seen in the cohort of relatives among carriers of the BRCA1 mutation, she said.

But even for women exposed to lower levels of whole-lung radiation (10 to 19 Gy), the cumulative incidence was elevated and was comparable to the 10% rate seen among carriers of the BRCA2 mutation in the cohort of relatives, she said.

While treatment for Hodgkin's lymphoma has changed to reduce the dose of radiation, therapy for other childhood cancers has not, Moskowitz said.

She said one implication of the findings might be that women given whole-lung radiation in youth should be offered regular breast cancer screening from an early age.

The findings are "rather striking ... and certainly warrant our careful consideration," commented Nicholas Vogelzang, MD, of the Comprehensive Cancer Centers of Nevada in Las Vegas and US Oncology, who was not part of the study but who moderated the ASCO press conference.

Vogelzang said it's important to improve both follow-up and screening for women given radiation therapy in youth.

"The benefit of curing a cancer is that you can live 25 or more years," he said, but the downside is the increased risk of later disease.

"We have an obligation to those thousands and thousands of young women we treated years ago, and hopefully this will increase our awareness of need for mammogram screening of this population," he said.

The studies were sponsored by the National Cancer Institute.

Moskowitz reported no relevant conflicts.

Reviewed by Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco

Accessibility Statement

At MedPage Today, we are committed to ensuring that individuals with disabilities can access all of the content offered by MedPage Today through our website and other properties. If you are having trouble accessing www.medpagetoday.com, MedPageToday's mobile apps, please email legal@ziffdavis.com for assistance. Please put "ADA Inquiry" in the subject line of your email.